Acquisition
The Surveyor is obtainable from the bandit leader of the Bandits on the Road encountered when first entering Lothering. If you choose to fight them, you will get a dialogue opportunity once the bandit leader's energy is down to about 25%. You can ask him to hand over everything they've stolen, or you can choose to kill him anyway and pick up the Surveyor ring from his corpse.
I killed the Leader and did not get this ring when looting the corpse on the Steam Ultimate edition PC version. So the best option would be to get the ring before killing him.